To evaluate the causes of abnormal brain functions in Myotonic Dystrophy. To see whether certain tests can help doctors understand why some patients with MD have abnormal brain function, especially when they have sleep apnea which involves breathing difficulties during sleep. GRAMT=M01RR004250667 To determine the sensations of the rectum and arm after being stimulated, how the brain reacts to these sensations and how sleep may be affected by these sensations.